The growing use of agent systems and the widespread penetration of the Internet has opened up new possibilities for scientific collaboration. We have been investigating the role for agent systems to aid with collaboration among Experimental High-Energy Physics (EHEP) physicists. A necessary component is an agreed ontology, which must include complex mathematical relations involving such quantities as the energy and momentum of elementary physics particles. We claim that the current web-ontology specification languages are not sufficiently expressive to be useful for explicit representation of mathematical expressions. We adapt some previous work on representing mathematical expressions to produce a set of mathematical representational primitives and supporting definitions that will allow knowledge sharing in agent systems. The paper sketches out a scheme for dealing with mathematical relations in scientific domain web-ontologies, illustrated with examples arising from our interactions with the EHEP physicists.